1. Field of the Invention
The subject disclosure relates to a control system for use with aircraft gas turbine engines, and more particularly to, a control system that includes a real-time vibration monitoring system having a diagnostic and a prognostic component.
2. Background of the Related Art
The gas turbine engine includes several concentrically mounted components, such as shafts, bearings and gears, each rotating at a slightly different and known frequency. Machinery having massive rotating components, such as jet aircraft engines, may experience shaft, bearing, and/or gear failures. In addition, these rotating components may become unbalanced and impose loads upon the bearings and engine housing well beyond acceptable specifications. These problems may be a result of any variety of causes which include, manufacturing defects, design defects, wear, misuse, accidental damages and the like. In the case of in-flight aircraft, failure of these engine components can lead to, not only engine loss, but a catastrophic loss of aircraft and crew.
Vibration amplitudes and patterns, induced by the rotation of jet engine sub-components, can be indicative of sub-component degradation and decreased reliability. Vibration detection is not only an invaluable safety tool used to monitor engines while in operation, but has been incorporated into scheduled engine maintenance procedures. Various techniques have evolved in the art to detect and analyze engine sub-component vibration amplitudes and patterns. For example, U.S. Pat. No. 4,488,240 to Kapadia et al. discloses a vibration monitoring system for gas turbine engines, which includes a non-recursive digital filter network controlled by a data processor. Digital techniques are used to process tachometer signals and general sampling signals at frequencies which are an integral multiple of the component rotating frequency. The output of the digital filter network is a signal used to drive a display device.
Systems such as that disclosed in the Kapadia et al. patent include various hardware and circuitry, for example, micro processors, multiplexers, analog signal conditioning circuitry, analog to digital signal converters, digital filters, digital to analog signal converter of output and a variety of memory chips.
Typically, a vibration analysis system consists of an analysis module which is connected to a generic vibration sensor located at the engine. In addition, the analysis module must access engine specific data for comparison and analysis. The analysis module may be integrally installed in an aircraft for monitoring vibrations during operation. The analysis module may be located in the engine housing or located somewhere else in the aircraft. The design considerations of the location of the analysis module may take into account optimal vibration sampling considerations and space constraints.
A disadvantage of prior art vibration monitoring systems is that they do not include a diagnostic component which is capable of comparing in real-time the measured vibration amplitudes for various shafts, bearings and gears to stored engine specific data. Additionally, prior art systems do not include a prognostic function wherein the time remaining to component failure is predicted based on the measure vibration levels for that component and stored engine specific data.
There is a need therefore, for a control system which includes a vibration monitoring system that has a diagnostic and a prognostic component and is capable of evaluating, in real-time, measured changes in the vibration amplitudes for multiple components.